Hold notification creation A/T cleanup module

Hold notification creation A/T cleanup module

New CreateHoldNotification Action/Trigger cleanup module that, when
linked to a hold-based event_definition, adds an entry into
action.hold_notification for each hold processed.  The main user-facing
change from this will be that the hold notification time / count in the
staff client will now take A/T notices into effect in addition to
manually created hold notifications.

Signed-off-by: Bill Erickson <berick@esilibrary.com>
Signed-off-by: Mike Rylander <mrylander@gmail.com>